The invention relates to an adhesive and to its use for an adhesive tape.
For industrial pressure-sensitive adhesive (PSA) tape applications it is very common to use adhesive tapes, which are required to withstand high temperatures. Some of the applications to which this applies are in the automotive sector. In that sector, particularly in the vicinity of the engine compartment, adhesive tapes are affected with particular severity by sharply fluctuating temperatures and by fuels. These properties are possessed in a very good form by crosslinked acrylate PSAs.
Additionally a very wide variety of substrates in the industrial sector may likewise be adhesively bonded. Here it may in some cases be of advantage to use heat-activable adhesives, which above a certain temperature soften, flow very effectively onto the substrates and then cool to form a solid bond.
In addition to the adhesive tapes already described there is an increasing demand—owing to more stringent environmental regulations, particularly for manufacturing—for particularly environment-friendly adhesive tapes which exhibit very little outgassing or none at all.
In order to achieve this for the requirements in the automotive industry, for example, two technologies are required for acrylate adhesive tapes. First the adhesive tapes ought not to contain resins, since resins evaporate out under prolonged temperature storage and so form deposits in the surrounding area. Secondly the adhesives ought to be prepared by the hotmelt technology: following polymerization, all of the remaining solvents and residual monomers are removed or stripped off and then the adhesive is crosslinked on the backing.
To date it is not proved possible to fulfil all of these requirements on the part of industry. U.S. Pat. No. 5,086,088, for example, describes thermally activable adhesives, and these adhesives on the one hand do not meet the requirements for low outgassing, owing to their composition and to the use of UV polymerization technology, and on the other hand cannot be processed from the melt, owing to the thermal curing agent present, since the thermal crosslinking reaction would be initiated even in the course of hotmelt processing.
It is an object of the invention to eliminate the disadvantages associated with the prior art. The intention is in particular to specify an adhesive which exhibits low outgassing and is fuel-resistant, which can be postcrosslinked under high temperatures, develops relatively high bond strengths and can be processed even from the melt. The intention is further to specify a use for an adhesive of this kind.